hi all,
naomi, in answer to your question, 'is it something we are overlooking?' I was having a look at JKR's website today and the wizard of the month is Godric Griffindor, it says that he was the first owner of the sorting hat, this could possibly be a clue, because Dumbledore says in The Half Blood Prince 'that the ONLY known relic of Griffindor remains safe.' but with the sword surely that makes TWO known relics.
If you remember in THBP, when Tom Riddle went to see Dumbledore for the DADA job, it says that 'For a second, Harry was on the verge of shouting a pointless warning: he was sure that Voldemort's hand had twitched towardsnhis pocket and his wand; but then the moment had passed'
Supposing Voldemort had used his wand and made the sorting hat into a horcrux, it is very possible as the sorting hat is always in Dumbledores office.
Any thoughts anyone?